I. Field of the Invention
This invention relates generally to waste reduction systems and more particularly to an improvement in an environmental chamber and a method of using same for composting and reducing solid waste.
II. Discussion of the Prior Art
Solid waste disposal has become a problem in many developed countries of the world. Existing landfills are reaching maximum capacity, and people oppose building new facilities due to pest and health hazards. Landfills contribute pollution to the surrounding land, air, and water. Leakage from the decomposing waste in the landfills enters the ground and adds toxic chemicals to the water table. If the landfill is close to the sea, run-off adds toxic chemicals to the ocean. Gases, such as methane and carbon dioxide, produced by decomposing waste are released into the atmosphere, contributing to the greenhouse effect. An alternative to landfills is needed to alleviate these problems.
Alternatives for decreasing reliance on landfills include burning the organic and inorganic waste for energy or composting the organic waste for fertilizer and recycling the inorganic waste. Producing energy by burning solid waste is also an attractive method. However, plastics are part of the waste, and when burned plastics release known carcinogens such as dioxin and chlorine. Although exhaust gases are scrubbed to remove toxins, the possibility of releasing them into the atmosphere still exists. A more cost-effective method of dealing with plastic waste is recycling.
Biodegrading organic waste produces material for supplementing soil fertilizer. During the decomposition process, typically methane, water vapor and carbon dioxide are released. These gases are usually released directly into the atmosphere. Instead, the methane and carbon dioxide should be trapped for later use or resale. The solid waste decomposition process is slow, taking several weeks before a final product is ready. To trap gases and speed up the biodegrading process, a closed loop environmental chamber can be used. In accordance with the present invention, a closed loop environmental chamber is configured to attain optimum conditions for decomposition. Plastic and other inorganic waste not broken down in the closed loop chamber are separated from the organic waste, reduced and sent to recycling centers for processing.
Systems for composting and separating organic waste from inorganic waste have been developed in the past. One process, described in U.S. Pat. No. 3,847,803, issued to Fisk, describes grinding the unsorted waste, treating the waste anaerobically to soften the biodegradable portion, separating the waste into biodegradable and non-biodegradable waste, treating the biodegradable waste aerobically in the presence of potassium and phosphorus, and curing the aerobically treated waste.
In the Fisk patent, the unsorted waste is treated anaerobically in one of three anaerobic predigestion tanks. The waste is held in the anaerobic predigestion tank for approximately three days. The tanks do not appear to thoroughly mix the solid waste or trap gases, such as methane, for later use. Instead, the Fisk patent warns that the dwell time of the waste in the anaerobic predigestion tanks should not extend beyond eight days, or methane gas will be produced. Thus, the process described in the Fisk patent does not accommodate the production of methane.
Fisk teaches that partially anaerobically decomposed waste be fed into a separation tank to separate the biodegradable waste from metal, glass, plastic, sand, grit, and other inorganic material. In the separation tank, fermentation causes the biodegradable waste to rise to the surface while the non-biodegradable waste settles to the bottom. The separation tank is not enclosed. Therefore, the gases and smells produced by the fermenting biodegradable waste are carried by the wind to neighboring communities.
In accordance with the Fisk patent, raw sewage is pumped into collecting tanks where enzymes are added. The Ph and temperature are regulated in the tanks to stimulate growth of aerobic bacteria for deodorizing the sewage. These tanks are enclosed cylinders. The treated raw sewage is thoroughly mixed with biodegradables taken from the separation tank. The resulting slurry is dewatered and transferred into the first of a series of three aerobic digestors, each having a one-day cycle.
The aerobic digestors are approximately 10 feet in diameter by 30 feet in height, having a spiral mixing auger installed vertically and extending almost the entire length of the tanks. The mixing auger is enclosed in an inner tube and conveys waste from the lower portion of the tank to the top. This agitation turns the biodegradable waste, allowing fungi to grow during the rest periods. The turned waste is subjected to gases that assist in decomposition and add value to the end product. Finally, the resultant material is transferred to a curing area where bacteria is sprayed on the finished product to add nitrogen and plant growth factor.
The process described in the Fisk patent does not trap carbon dioxide or methane. Gases produced during the fermentation process are released directly into the atmosphere. Metal and plastic are recovered using various sifters, but no reduction of the plastic or metal is described.
The present invention provides a method and a closed loop environmental chamber for trapping and extracting methane, carbon dioxide and other gases released during decomposition of the biodegradable waste or, in the alternative, ethanol as a fermentation byproduct. The method and environmental chamber of the present invention are also used for reducing plastic and metal to basic components for later reclamation.
Systems for producing and trapping methane are present in the prior art. U.S. Pat. No. 4,252,901, issued to Fischer et al., and U.S. Pat. No. 4,511,370, issued to Hunziker et al., each disclose a process for anaerobic decomposition of biodegradable waste to produce methane, carbon dioxide and a residual sludge material. However, neither of the patents disclose separating and reducing plastic or metal.
Methods for converting biodegradable waste and recovering gases usually use a series of tanks, often partially embedded in the ground, to hold the solid waste slurry. These tanks almost always have some means of agitating or mixing the slurry to achieve a uniform temperature and distribute the bacteria and chemicals used to promote decomposition. One method employed for agitating or stirring the solid waste slurry is rotating a horizontal rotary disk in a vertical tank. Another method employed is to introduce biogas to create a pneumatic thrust that causes a flow in the solid waste slurry.
U.S. Pat. No. 4,514,297, issued to Enqvist, describes a reactor for the anaerobic decomposition of organic sludge and the production of methane. The reactor comprises an essentially horizontal cylinder having an agitator rotating around a central horizontal shaft. At the top of one end of the reactor is an inlet port for introducing sludge, and at the top of the other end is an outlet port for discharging digested waste. Outlets for recovering methane are in the upper portion of the reactor.
The amount of sludge introduced at the inlet port and returned from the outlet determines the rate of flow through the reactor. The level of the sludge must be maintained above the central horizontal shaft to achieve flow. To maintain the desired level, the sludge presented at the inlet port must be externally regulated. Mixing blades on the agitator for moving the sludge from the middle or bottom of the reactor to the top do not regulate the rate of flow of sludge through the reactor.
The present invention provides an environmental chamber comprising a rotatable cylindrical container having directional vanes disposed inside the container. The pitch of the directional vanes can be changed from outside the container. The rate of flow of sludge through the chamber is regulated by the speed of rotation of the container and the pitch of the directional vanes. Fluids, gases and solid waste are introduced or discharged from the chamber through a plastic seal bearing, while the chamber rotates. The plastic seal bearing may be made from a high strength, resilient, synthetic material, such as nylon or a waxy material such as that sold by E. I. Du Pont De Nemours and Company under the trademark TEFLON.RTM. Methane carbon dioxide, ethanol and other fermentation gases and fluids are trapped for later use or resale. The present invention allows for independent regulation of the rate of flow of sludge through the chamber and uses only one type of environmental chamber for organic decomposition and reducing metal and plastic to basic components.
From the above analysis, it can be seen that the prior art references of which I am aware, individually and as a whole, do not disclose a method for reducing solid waste using one type of environmental chamber for aerobic decomposition, anaerobic decomposition, reducing plastic, and reducing metal, or an environmental chamber that provides for independent regulation of the rate of flow of waste through the chamber.